The present invention relates to Z-axis gradient coils for use in a nuclear magnetic resonance (NMR) system and, more particularly, to novel Z gradient coils fabricated from etched conductors on an insulative substrate, and eliminating the need for winding machines or multiple connection soldering.
A NMR system typically requires that gradient magnetic fields be provided along each of the three orthogonal axes of a Cartesian coordinate system. Typically, each magnetic field gradient is provided by a different coil, or coil set. In a system wherein the static magnetic field B.sub.O is provided in the axial Z direction, the coils for providing a gradient in the transverse (X-Y) direction are relatively easily fabricated by etching a particular pattern onto a copper circuit board, which is then bent into the form of a cylinder for lining the bore of a B.sub.O -generating main magnet. However, the coil, or coil set, for generating the Z-axis magnetic field gradient has typically been fabricated of separate wires, wound on a special winding machine; it was previously thought to be topologically impossible to make the Z-gradient winding from copper circuit board without requiring multiple solder connections to complete the circuit in a circumferential direction. From a manufacturing viewpoint, it is obviously desirable to be able to fabricate all three gradient windings by the same method; this is particularly true of sets of gradient coils for small bore NMR systems, where precision positioning of, and soldering between, ever-smaller wire conductors is difficult and the cost of etched coils is, due to the smaller size, no longer an issue. It is therefore highly desirable to provide an etched conductor Z-gradient field-producing winding, or winding set.